The present invention relates to an apparatus permitting the treatment of bodily conduits in the area of a bifurcation, that is to say in the area where a principal conduit separates into two secondary conduits. It also relates to equipment for positioning this apparatus.
This apparatus can be used for the treatment of vascular bifurcations, in particular the carotid, femoral, iliac, popliteal, renal or coronary bifurcations, or nonvascular bifurcations, such as tracheal or biliary bifurcations, for example between the common bile and cystic ducts, or in the area of the bifurcation of the principal bile tract.
The treatment can consist in re-establishing the appropriate diameter of the bifurcation, in cases of arteriosclerosis or internal cell proliferation, in rectifying a localized or nonlocalized dissection in the wall of the conduit, or, in cases of aneurysm, in recreating a bifurcation of normal diameter, while eliminating the aneurysmal pouch.
It is known to treat narrowing of a rectilinear blood vessel by means of a radially expandable tubular device, commonly referred to as a stent. This device is introduced in the unexpanded state into the internal lumen of the vessel, in particular by the percutaneous route, as far as the area of narrowing. Once in place, it is expanded in such a way as to support the vessel wall and thus re-establish the appropriate cross section of the vessel.
The device can be made of a nonelastic material, and in this case is expanded by means of an inflatable balloon on which it is engaged, or can be self-expanding, that is to say made of an elastic material, expanding spontaneously when withdrawn from a sheath which is holding it in the contracted state.
U.S. Pat. Nos. 4,733,665 and 4,886,062 are illustrative of existing devices and of corresponding positioning techniques.
A conventional stent is not entirely suitable for the treatment of a narrowing situated in the area of a bifurcation, since its engagement both in the principal conduit and in one of the secondary conduits can cause immediate or delayed occlusion of the other secondary conduit.
It is known to reinforce a vascular bifurcation by means of a device comprising two elements, each formed by helical winding of a metal filament. One of the two elements has two parts of diameter corresponding respectively to the diameter of the principal vessel and to the diameter of one of the secondary vessels, and is intended to be engaged on the one hand in this principal vessel and, on the other hand, in this secondary vessel. The other element has a diameter corresponding to the diameter of the other secondary vessel and is coupled to the first element, after the latter has been put into place, by engaging one or more of its turns in the turns of the first element.
This equipment permits reinforcement of the bifurcation but appears unsuitable for treating a vascular narrowing or an occlusive lesion, in view of its structure and of the low possibility of radial expansion of its two constituent elements.
Moreover, the shape of the first element does not correspond to the shape of a bifurcation, which has a widened transitional zone between the end of the principal vessel and the ends of the secondary vessels. Thus, this equipment does not make it possible to fully support this wall or to treat a dissection in the area of this wall.
In addition, the separate positioning of these two elements seems relatively difficult.
The present invention aims to overcome these various disadvantages by making available apparatus with which it is possible to treat a pathological condition in the area of a bifurcation, by fully supporting the vascular wall and by being relatively simple to position.
The apparatus to which the invention relates comprises, in a manner known per se, segments delimiting longitudinal conduits, one of which is intended to be engaged through the bifurcation, and another of which is intended to be engaged in a secondary conduit of this bifurcation.
According to the invention, this apparatus comprises:
at least one radially expandable segment which has, in a predetermined expanded state, a cross section substantially greater than the cross section of one of the secondary conduits; and
a segment which has, in a predetermined expanded state, a truncated shape, corresponding to shape of the bifurcation in the area of the widened transitional zone which separates the principal conduit from the secondary conduits.
In some embodiments of this invention, this apparatus further comprises a flexible link between these two segments.
For the sake of simplification, the segment which has, in the expanded state, a cross section substantially greater than the cross section of one of the secondary conduits will be referred to hereinafter as the xe2x80x9csecondary segmentxe2x80x9d, while the segment which has, in the expanded state, a truncated shape will be referred to hereinafter as the xe2x80x9ctruncated segmentxe2x80x9d.
The secondary segment is intended to be introduced into the secondary conduit in the contracted state and to bear, in the expanded state, against the wall of this conduit. This expansion not only makes it possible to treat a narrowing or a dissection situated in the area of this conduit, but also to ensure perfect immobilization of the apparatus in the conduit.
In this position of the device, the truncated segment bears against the wall of the conduit delimiting the widened transitional zone of the bifurcation, which it is able to support fully. A narrowing or a dissection occurring at this site can thus be treated by means of this apparatus, with uniform support of the vascular wall, and thus without risk of this wall being damaged.
The two segments orient themselves suitably in relation to each other upon their expansion.
Preferably, at least the truncated segment is covered by a wall which gives it impermeability in a radial direction.
This wall makes it possible to trap, between it and the wall of the conduit, the particles which may originate from the lesion being treated, such as arteriosclerotic particles or cellular agglomerates, and thus to avoid the migration of these particles in the body.
Moreover, the apparatus can permit treatment of an aneurysm by guiding the liquid through the bifurcation and thereby preventing stressing of the wall forming the aneurysm.
The segments can be made from tubes of material of a different diameter, with the tube for the truncated segment having a larger diameter than the tube for the secondary segment. The tubes may be comprised of the same material. The use of tubes of different diameters results in the truncated segment having a larger radial force, especially at larger diameters.
The apparatus can comprise several secondary segments, placed one after the other, to ensure supplementary support of the wall of the secondary conduit and, if need be, to increase the anchoring force of the device in the bifurcation. To this same end, the apparatus can comprise, on that side of the truncated segment directed toward the principal conduit, at least one radially expandable segment having, in the expanded state, a cross section which is substantially greater than the cross section of the principal conduit.
These various supplementary segments may or may not be connected to each other and to the two aforementioned segments by means of flexible links, such as those indicated above.
The flexible links can be integral with one of the segments and separately connected to the other segment, or the flexible links can be separate pieces of material separately connected to both segments, such as by welding.
Preferably, the flexible link between two consecutive segments is made up of one or more bridges of material connecting the two adjacent ends of these two segments. Said bridge or bridges are advantageously made of the same material as that forming the segments.
According to a preferred embodiment of the invention, each segment has a meshwork structure, the meshes being elongated in the longitudinal direction of the device, and each one having a substantially hexagonal shape; the meshes of the truncated segment have a width which increases progressively in the longitudinal sense of the device, in the direction of the end of this segment having the greatest cross section in the expanded state.
This increase in the width of the meshes is the result of an increase in the length of the edges of the meshes disposed longitudinally and/or an increase in the angle formed between two facing edges of the same mesh.
In addition, the truncated segment can have an axis not coincident with the longitudinal axis of the secondary segment, but oblique in relation to this axis, in order to be adapted optimally to the anatomy of the bifurcation which is to be treated. In this case, the widths of the meshes of the truncated segment also increase progressively, in the transverse sense of the device, in the direction of a generatrix diametrically opposite that located in the continuation of the bridge connecting this segment to the adjacent segment.
The apparatus can be made of a metal with shape memory, which becomes malleable, without elasticity, at a temperature markedly lower than that of the human body, in order to permit retraction of the apparatus upon itself, and to allow it to recover its neutral shape at a temperature substantially corresponding to that of the human body. This metal is preferably the nickel/titanium alloy known by the name NITINOL.
The equipment for positioning the apparatus comprises, in a manner known per se, means for permitting the expansion of this apparatus when the latter is in place. These means can comprise a removable sheath in which the device is placed in the contracted state, when this device is made of an elastic material, or a support core comprising an inflatable balloon on which the device is placed, when this device is made of a nonelastic material.
In either case, this equipment comprises, according to the invention, means with which it is possible to identify, through the body of the patient, the longitudinal location of the truncated segment, so that the latter can be correctly positioned in the area of the widened zone of the bifurcation.
In the case where the expansion of this same segment is not uniform in relation to the axis of the device, the equipment additionally comprises means with which it is possible to identify, through the body of the patient, the angular orientation of the device in relation to the bifurcation, so that that part of this segment having the greatest expansion can be placed in a suitable manner in relation to the bifurcation.